Our body converts β-carotene into ____.

A provitamin (or vitamin precursor) is an inactive compound obtained from food that the body converts into an active vitamin through its own metabolic enzymes — unlike a vitamin that already arrives in an active or near-active form and needs no further conversion.

Beta-carotene is the principal dietary provitamin A carotenoid, found in orange, red, and dark-green vegetables. In the intestinal mucosa and liver, the enzyme beta-carotene 15,15'-monooxygenase cleaves one molecule of beta-carotene (a symmetric 40-carbon tetraterpenoid) at its central double bond into two molecules of retinal, which is then reduced to retinol or oxidised to retinoic acid — together, these active forms constitute vitamin A. This conversion is the main dietary route to vitamin A for people eating carotenoid-rich vegetables such as carrots, spinach, pumpkin, and sweet potato instead of preformed retinol from animal foods.

• Vitamin K (phylloquinone/menaquinone) comes directly from leafy vegetables or gut-bacterial synthesis — it is not built from carotenoid cleavage.

• Vitamin E (tocopherols/tocotrienols) is a separate phenolic isoprenoid compound from plant oils and is not produced from carotenoids.

• Vitamin C (ascorbic acid) is synthesised by plants from glucose via the uronic-acid pathway; humans lack the final enzyme in that pathway and get vitamin C only from diet, with no carotenoid step involved.

Only vitamin A is generated in the body by enzymatic conversion of beta-carotene, confirming that the correct answer is vitamin A.